The invention relates to a redetachable, self-adhesive device which can be released again from its adhesive bond without leaving any residue by pulling on the adhesive film, arranged on it, in the direction of the bonding plane. In particular, the invention relates to a plate of this type, on which other things can be fastened if appropriate, or which itself is designed as a hook or the like if appropriate.
Such devices, in particular hooks, are known. For instance, DE 42 33 872 C2 describes a redetachable, self-adhesive hook which is equipped with an adhesive film which can be adhesively released by pulling and which is commercially available as xe2x80x9ctesa(copyright) Power-Strips with Hooksxe2x80x9d. A so-called system hook with base plate and attachable decorative hook is also commercially available as the tesa(copyright) Power Strip System Hook.
WO 94/21157 also discloses such a hook, which differs from the abovementioned hook in particular by the use of an adhesive film of the kind which is highly extensible and at the same time does not recover its original form.
In the practical use of such devices, problems may occur, however, in particular during later detachment.
What is particularly disadvantageous about the previously known problem solutions is that the releasing of the adhesive bond has to take place by pulling the adhesive strips substantially in the bonding plane, errors in use being inevitable for the unexperienced user.
In many cases it has been found that tears are caused by the user exerting considerable force to press the item to be released against the object to which it is adhesively bonded during the releasing process. As a result, the force necessary for pulling the adhesive tape out of the adhesive joint is increased to such an extent that the tearing resistance is exceeded, with the unfortunate consequence for the user that the adhesive tape tears and the adhesive bond can no longer be released non-destructively and without leaving any residue.
This object is achieved by means of a device such as that characterized in more detail hereinbelow. Accordingly, the invention relates to:
A redetachable, self-adhesive device having a plate, the sides and/or front side of which have fastening means, if appropriate, and the rear side of which has a strip of an adhesive film which is adhesive on both sides and is adhesively attached in such a way that one end of the adhesive film strip protrudes beyond the plate as a grip, the adhesive film being of such a kind that the adhesive bond achieved with it can be released again by pulling in the direction of the bonding plane, stretching the strip, characterized in that the rear side of the plate (1) has laterally alongside the adhesively attached adhesive film (5) spacers (3A, 3B), the height of which is less than the thickness of the adhesive film (5).
In particular a device as described hereinabove characterized in that the spacers (3A, 3B) are located on both sides alongside the adhesively attached adhesive film (5).
In particular a device as described hereinabove characterized in that the spacers (3A, 3B) are formed as fillets or segments.
In particular a device as described hereinabove characterized in that the spacers (3A, 3B) are arranged on both sides and, on each of these sides, at least in the region of the two ends.
In particular a device as described hereinabove characterized in that it is formed as an injection-molded part of plastic.
In particular a device as described hereinabove characterized in that the height of the spacers (3A, 3B) is 35-90% of the thickness of the adhesive film (5), in particular 0.3-0.6 mm in the case of a thickness of the adhesive film (5) of 0.65 mm.
In particular a device as described hereinabove characterized in that the adhesive film strip (5), with or without an intermediate substrate, is elastically or plastically extensible.
In particular a device as described hereinabove characterized in that the adhesion of the adhesive film (5) is less than the cohesion, the adhesiveness is dissipated to a great extent when the film is extended, and the ratio of pulling-off force to tearing load is at least 1:1.5, the adhesive film being of the kind which is based on thermoplastic rubber and tackifying resins, with high elasticity and low plasticity.
In particular a device as described hereinabove characterized in that the rear side of the adhesive film (5) is covered with a release laminate, such as a siliconized release paper or a release film.
In particular a device as described hereinabove characterized in that at the sides of the plate (1) there are engaging devices (4) into which a corresponding hook or the like can be engaged.
The height of the spacers is advantageously chosen such that it is less than the thickness of the (unstretched) adhesive film, so that a satisfactory adhesive bond with the adherent surface is possible. The extension of the adhesive film occurring during the detachment operation causes the said film to be reduced correspondingly in width and thickness. If the thickness of the adhesive film reached during detachment is less than the height of the spacers, detachment of the adhesive film without tearing is even possible if high contact pressures occur at the same time vertically to the adhesive bond, which would otherwise have lead to tearing of the adhesive tape.
According to the invention, suitable in particular as adhesive films are those corresponding to DE 33 31 016, DE 42 22 849, DE 42 33 872, WO 92/11333 and WO 94/21157.
For instance, DE 33 31 016 A1 describes an adhesive film for re-releasable adhesive bonds which allows an adhesive bond established therewith to be released by pulling on the adhesive film in the direction of the bonding plane. With such adhesive films, high adhesive forces and shear strengths can be achieved and adhesive bonds can be released again without further aids, in a way comparable to the opening of a preserving jar, similar to the way in which there the rubber seal is pulled by the grip out of the seal joint.
DE 42 22 849 C1 describes such an adhesive film with a TV-impermeable grip.
WO 92/11333 also describes, inter alia, adhesive films for corresponding applications, the adhesive films used having a low elasticity with at the same time high extension.
Double-sided self-adhesive tapes with a foam intermediate substrate, for example of polyethylene foam, can also be used according to the invention.
In general, for production, processing and handling of the particularly preferred adhesive films, reference is made to DE 33 31 016, DE 42 22 849 and WO 92/11333.
Suitable as the material for the plate or moulding, in particular for base plates, are:
Plastic, metal, wood (coated, for example painted, and uncoated), ceramic and the like.
Devices according to the invention serve for receiving one side of the adhesive film, the other side of which is adhesively bonded onto the selected under-lying surface. A wide variety of adapters, including hook bodies, can be placed onto the device or plate. To produce a high bonding strength, the surface of the plate on the side to which the adhesive film is applied consists in particular of a material which has an adhesion with respect to the adhesive film which is adequate for the respective application. When using contact adhesives based on styrene block copolymers or acrylate copolymers, advantageously used in this case are, inter alia, polystyrene, impact-modified polystyrenes, PMMA, aromatic polyesters, polycarbonate or polyamide.
To accomplish a pulling-off behaviour without tearing, even under the effect of high forces acting perpendicularly with respect to the bonding plane (for example caused by high contact pressure when releasing the adhesive bond), the plate is equipped with spacers (for example fillets), as still to be described in detail, on the side which bears the adhesive film.
Spacers may be provided on both sides alongside the adhesive film over the entire length of the base plate, or else only in certain subregions thereof. Specific formations, right-angled fillet-like, rounded-off fillet-like, punctiform etc., are possible.
Tests with different redetachable adhesive films show that, depending on the type and structure of the adhesive films used, typical stripping extensions lie between 100% and 800%. In practice, it is found that, in the case of substantially rubber-elastic adhesive films, the height of the spacers should be at least about 0.05 mm, preferably 0.10 mm, higher than the thickness of the stretched adhesive films during the detachment process. For a reliable adhesive bond, on the other hand, the spacer height should be kept about 0.05 mm, preferably 0.1 mm, particularly preferably 0.15 mm, less than the thickness of the adhesive films in the non-stretched state. The values specified relate to planar, solid adherent surfaces. In the case of rough and/or slightly deformable adherent surfaces, values higher than those quoted may be advisable both for a satisfactory bonding process (adequate contact pressure) and for satisfactory redetachment.